Body function sensors



1964 E. A. GRINDHEIM ETAL 3,154,066

BODY FUNCTION SENSORS Filed Oct. ll, 1961 JfA/SOR /0 23 c l Z5 54/ '26 5 AMP. E1 7.

24 55 INVENTORs.

ug/M; 41m moimi Un t d S ws Pa en 3,154,066 BODY FUNCTION SENSORS Earl A. Grindheirn, Arthur J. Stenstrorn, and Richard L. ,Walus, all of Minneapolis, Minn., assignors, by mesne assignments, to Robert L. Gannon, Minneapolis, Minn.

Filed Oct. 11, 1961, Ser. No. 144,386 6 Claims. (Cl. 128---2.05)

' This invention relates to the field of electro-mechanical sensors and more particularly to the field of sensors for detecting functions of the human body.

In a good many instances, it is desirable to detect certain body functions of patients in hospitals under treatment and patients who may be under certain emergency conditions where the body function information can best be used by displaying the information for medical personnel or recording it for future use. ln'either situation, the information received in the form of signals from the senors is generally amplified and displayed, or recorded for future use in establishing a medical history for the patient. It is also quite important to establish a proper medical history where the patient may be in a post-operative room, where the body function information is not only needed for future references, but should also be available to be displayed and aid in a proper recovery of the patient. Under certain other emergency conditions, such as encountered in emergency rooms in hospitals, and where patients are being transported to a hospital due to sickness or injury, it is also highly desirable to have the body function information available in order to determine the conditions of the patient. Two of the most desirable body functions for which information is easily obtained, are the detection of the bloodpulse of the patient which can be compared to a time base to determine the pulse rate, and the respiratory cycle or function which can be compared to a time base to determine the respiratory rate, or rate of breathing. Where the body functions of the patient have slowed or are relatively weak, due to the weakened conditions of the patient, the problem is especially magnified since- From this standpoint, it is highly desirable that anyj sensors which may be used in conjunction with the patient for detecting their body functions be of the type that can' be left unattended after being attached to the body or' body members.

Certain laboratory instruments are adaptable for sensors under some of the conditions set forth above, but it has been found that they are generally quite cumbersome and sometimes bulky in their use and therefore. they do not lend themselves for portable or emergency use. As mentioned previously, the most common prac tice is to have a person use his own. sensory facilities to,

detect the body functions required, and thus it generally requires two people to actually perform the treatment to the patient, yet one merely acts in a manner to supply the information about the patients body functions. v The present invention would, upon proper application, provide the necessary information for the attending medical personnel to aid in their treatment of the patient without having to resort to the disadvantage just described which is genenally encountered in the present day methods of treatment. The present invention contemplates using a deflection measuring device, generally in the form of a strain gauge, to detect minute changesin the body or "ice - to provide a new and improved body function sensor.

It is a further object of the present invention to provide a sensor using strain gauges for detection of the body function to be sensed.

It is still another object of this invention to provide a sensor for sensing changes in a body member volume caused by the body function to be detected.

It'is still a further object of the present invention to provide a new and improved sensor for detecting the respiratory function of the human body.

It is yet another object of this invention to provide a new and improved sensor for detecting the blood pulse of the circulatory system of the human-body.

It is still another object of the present invention to provide a new and improved body function sensor using a magnification means to increase the strain gauge deflection.

It is yet another object of this invention to provide a body function sensor which is easily attached to, and re moved from, the body or body member which is not painful to the patient.

It is yet a more specific object of the present invention to provide a body function sensor which may be attached to the rib'cage to produce a signal representative of the respiration function of the body.

It is still another object of the present invention to provide a body function sensor which may be attached to fingers and toes of the body to produce a signal representative of the blood pulse rate.

It is a further object of the present invention to provide a body function sensor to be used with electrical apparatus to produce a signal for energizing an indicator.

These and other objects and advantages of our invention will more fully appear from the following description, made in connection with the accompanying drawings, wherein like reference characters refer to the same or similar parts throughout the several views, and in which; 7

FIG. 1 is atop view of a blood pulse sensor with the top portion of a rubber jacket removed along section I line 2 2;

FIG. 2 is a sectional view of FIG. 1 taken along section lines 1'1;

FIG. 3 is a modification of the blood pulse sensor shown in FIGS. 1 and 2 employing a lever for amplifying the movement ofv the deflection member and is shown in section with one side of the housing removed;

FIG. 4 vis an. isometric view of the respiration rate sensor; p

FIG. 5 is a sectional view taken from the top of FIG. 4 along lines 5--5; v

. FIG. 6 is a diagrammatic view of a portion of a patients chest cavity showing the respiration rate sensor in place for measuring the body functions; and

1 FIG. 7 is an electrical block diagram showing the electrical apparatus used with the sensor to produce an indication of the body function being detected.

' In describing the operation of a sensor which will detect a change in volume of the body element due to an increase in volume caused .by a slight pressure change in the blood circulatory system or due to the breathing j process, it may be well to briefly set forth the ease with which the device may be used upon the body for sensing the operation of the bodys blood circulatory system or respiratory system.

The thumb and fingers of the hand are supplied by the radial and ulnar arteries. In the thumb, the princeps poll-icis artery extends along the ulnar side of the metacarpal bone of the thumb to the first phalanx where it divides into two branches and runs along the sides of the thumb. The fingers receive a blood supply through the volaris indicis radialis arteries which are supplied by the radial arteries and through the volar digital arteries supplied by the ulnar artery. The volar digital arteries are divided into a pair of arteries which run along the contiguous sides of the index, middle, ring, and little fingers,

where they interconnect freely in the subcutaneous tissue back of the second and third phalanges, including the matrix of the fingernail. The toesof the feet are supplied mainly by the continuation of the anterior tibial artery which divides into two branches that extend tov the toes. The metatarsal arteries then supply the blood to the toes. In addition, the deep plantar artery supplies additional blood to the greater or big toe. Also, the posterior artery terminates in the medial plantar artery to supply the big toe and in the plantar metatarsal arteries to supply the toes where each artery divides into a pair of plantar digital arteries which supply the adjacent sides of the toes. Thus it can be, seen that even though the arteries are at the extreme ends of the body extremities, that there should be a direct communication line through the blood pressure system from the heart to the arteries just described. Keeping in mind, that the heart acts like a pump and the arteries act like hydraulic lines, it can be seen that the pressure will increase in the arteries with each pulsating movement of the blood from the heart into the arterial system.

The basic ditficulty in finding a sensor to sense. the movement of the abdominal wall due to breathing, is that there is no base member or reference, member to which something may be attached and yet supply the proper signal for determining the respiratory functions of the body. However, by using the rib cage along the edge where the costal cartilages of the ribs are connected to the sternum, a relatively fixed base or reference position may be established withv which to measure deflection of the abdomen. Thus the abdominal area which contains the obliquus externus and internus muscles actually moves with respect to the rib cage and therefore the volume of the body member about a particular cross section actually increases and decreases as the breathing process takes place. Therefore, the abdominal wall con.- tracts and expands with the breathing process, and with respect to the rib cage which is relatively fixed.

A sensor 10 has a supporting member 11 formed in an elongated elliptical shape with a central opening 12 formed therein. Supporting member 11 may also be thought of as a U shaped member in which an additional cross member 13 is formed between the open ends.

Cross member 13 has a bevelled edge 14 which slopesv downwardly and towards, the bottom of central opening 12. Supporting member 11 and cross member 13 may be.

formed of any light metal material or plastic material which is not readily deformable and retains its general shape. The outer side of cross member 13 is recessed slightly so that a terminal board 15 may be fastened to cross member 13 by a suitable means such as a screw 16. A deflection member 17 is fixedly fastened to cross member 13 by suitable means such as screws 18 and is of such shape as to follow the sloping contour of bevelled edge 14 and extend longitudinally downward through central opening 12. For the particular embodiment shown, the general longitudinal shape of the deflection member is similar to a capital I. Fastened as just described, deflection member 17 acts in the same manner as a cantilever member or element. In order to form a proper contact portion for the end of deflection member 17, a hemispherically shaped button 19 is fixedly fastened to the end of the deflection member. This may be accomplished by peening over the end of button like member 19 or through other suitable means. Attached along the longitudinal axis of deflection member 17, is a strain gauge 20 and the strain gauge may be attached by cement or some other bonding agent which fixedly fastens strain gauge 20 to the deflection member 17. Deflection member 17 may be formed of spring steel or certain types of beryllium copper may be used to form the spring element. It has been found that strain gauges of the silicon type having a large piezo effect prove to be quite successful for measuring the deflection of deflection member 17. Such strain gauges employing the piezo effect, when subjected to mechanical stresses, the electrical properties of the particular element are changed and therefore when connected in a proper circuit produce a desirable signal output. Certain strain gauges of the silicon type are laminated between plastic strips or may be covered by a plastic strip to protect the strain gauge element from me chemical and chemical deterrent etfects during its use and operation. When the strain gauge is contained in the laminated plastic sheets, the sheets are then fixedly fastend' to the deflection member. A pair of conductors 21 and 22 are connected to the electrical terminals of strain gauge 20 and are terminated in a pair of terminals 23 and 24 respectively. A pair of conductors 25 and 26 are connected to terminals 23 and 24 respectively to produce the necessary electrical change in the electrical circuit to which the sensor may be connected. Surrounding the entire supporting member 11 andv following the general contours of the protruding hemispherical button 19, is a rubber or plastic jacket 27. Jacket 27' is used to protect the strain gauge element 20 and to protect the patient from any toxic effects between the supporting element 11 and button like member 19.

A variation of the above described sensor is shown in FIG. 3 in which a supporting member 28 is of elongated elliptical shape and has a central opening 29 formed therein. The bottom of supporting member 28 extends longitudinally and substantially at right angles to the edges of supporting member 28 to form a portion which generally bears. against a body member such as a finger 30 or other such member as a thumb or toe. Adjacent to the edge of central opening 29 is a portion of supporting member 28 which forms a bevelled edge 31 which slopes downwardly towards the bottom of opening 29. Deflection element. 17 is attached. to the bevelled edge with screws 18 suchv as. shown in FIGS. I and. 2 and strain gauge element 20 is.

also connected to deflection element 17 in. the same man.- ner as just described, The. electrical connections. are the same as those previously mentioned to produce a proper signal output. A lever arm. 32 is pivotally supported by a pin 33 above the bevelled edge area and extends downwardly into opening 29 where. the lever arm has an end 34' that. is flat and substantially parallel with the bottom of supporting, member 28.. It is the flat portion 34 that engages the finger 3.0 or other such element as the thumb or toes. Pin 33 is. transverse to. the axis of the deflection member 17. and the lever arm at. its. end opposite the flat portion 34,v terminates in a sleeve 35. A lug 36 isfixedly fastened to the end of deflection element 17 at or about the same location that button member 19 is fastened to the sensor shown in FIGS. 1 and 2, and sleeve 35 andlug 36 have holes formed therein which have their longitudinal axis aligned with pin 33 to receive a pair of pins 37 and 38 which engage a link 39 to'mechanically join lever arm 32 with deflection member 17. It will, of course, be understood that different mechanical connecting means may be employed between lever arm 32 and deflection element 17, in fact, the upper end of lever arm 32 may simply be bent over to engage deflection element 17 and bear against it to deflect strain gauge 20. A releasable binding means 40 such as adhesive tape, webbing, or other suitable means may be used to hold supporting member 28 in place over the thumb or finger, or toe to cause a deflection of member 17 through the mechanical amplification of lever arm 32 in cooperation with deflection member 17.

The body function sensor is shown in its simplest form in FIGS. 4 and in which a sensor 41 is shown that is generally used for checking the respiratory function of the body. This sensor is encapsulated in a rubber mold 42 and contains therein, a deflection member 43 to which is attached a strain gauge 44 in a manner such as that just described. A terminal board 45 is fastened to one end of deflection element 43 by suitable means such as rivets 46 and a pair of terminals 47 and 48 are fastened therein. A conductor 49 connects one end of strain gauge 44- to terminal 47 and a conductor 59 connects the other end of strain gauge 44 to terminal 48. A pair of leads 51 and 52 are connected to terminals 47 and 48 to carry the current to strain gauge 44 and produce the appropriate signal for the apparatus to which it is connected. It will be observed that the end of deflection element 43 bearing terminal board 45 is of a more rigid construction due to the assembly of the two parts and it is this portion of the sensor which is fastened over the costal cartilages of the rib cage. It will be seen that the construction of the deflection element 43, the strain gauge 44, and the associated conductors and terminals are similar to those shown in the preceding figures and are formed of the same materials and operate in the same manner.

FIG. 6 shows a partial diagrammatic view of the rib cage where the costal cartilages of the ribs are beneath the skin of the body and to which is attached sensor 41 by suitable means such as tape. It will be noted that the end of sensor 4-1 which carries conducting leads 51 and 52 is over the rib cage area and the other end of sensor 41 is taped or fastened to the abdominal wall so that it may be flexed by the breathing process which in effect causes a temporary increase in the volume of the chest cavity at that location.

Operation In order to produce an indication of a deflection of deflection member 17 caused by a temporary increase in the volume of the body member, conductors 25 and 26 are connected to an amplifier 54 and a voltage source 55 respectively. Voltage source 55 may be either an alternating or direct voltage, and is also connected to amplifier 54 through a lead 56 to complete the input circuit and upon the signal being amplified by amplifier 54, an output signal is produced which illuminates a lamp 57 so that the instant the heart beat or respiratory function takes place, it will be so indicated by lamp 57. It will be obvious that other types of indicators may be employed such as an audible indication or other visual indication, or the signal may be applied to some form of recorder where the signals are recorded on a time base. As indicated previously, in the description of the circulatory system, the skin surrounding a thumb or finger such as 30 encloses certain annular muscle fiber which also surrounds the central bone and arteries contained therein. When some form of binding means is drawn around sensor or around its variation shown in FIG. 3, it will be seen that button member 19 or flat portion 34 of lever arm 32 is drawn snugly against the body member so that the spring like deflection member 17 is deflected. Since the skin of the fingers and thumb, and toes is drawn closely to the bony structures of these digits, at the joints, it will be seen that where the meaty structure lies within the digits, that there is substantially a fixed volume. Upon a heart beat or pulse producing a temporary increase in the blood pressure through the arteries, deflection member 17 is deflected slightly to produce a change in the deflection amount and this change is detected by strain gauge 20.

Because of the slight increase in pressure Within the arteries, the volume increases temporarily and then returns to its original volume and configuration upon the absence of the heart beat while the blood is being dissipated through the ends of the arteries within the fingers and toes. Since the strain gauges of the type just described are extremely sensitive, a slight change in the resistance of the element is easily created, which when placed in an electrical circuit changes the characteristics of the electrical wave shape. Since strain gauge 20 does change its resistance characteristics, it is represented as a variable resistance in FIG. 7. In attaching the sensors to the toes, fingers or thumb, it is not necessary to draw the sensors extremely tight against the body members, in fact, if drawn too tightly, the sensor will not operate properly because the member will not be allowed to expand along its outer peripheries due to a change in volume underneath the contacting part of the sensor.

Sensor 41 may be used equally well with the circuit shown in FIG. 7 to determine the respiration rate by counting the pulses for a given period of time due to the breathing process. Since the end of deflection member 43 is more or less rigid on the end containing terminal board 45, it is quite important that this end be at tached near the edge of the rib cage and the other end extended out over the abdominal cavity so that deflection member 43 and strain guage 44 will be under continuous movement as the breathing process takes place.

From the foregoing description of the invention, it will be seen that a body function sensor has been provided which is extremely sensitive and does not require an elaborate apparatus for attaching it to a member of the body. It may be used for sensing the cyclatory operation of the body circulatory system and the body respiratory system. Because of its rather simple construction, it is extremely reliable and may be used to provide a signal for various types" of indicators or recorders. The structure of the body function sensors is designed to detect the slight change in volume of the member to which it is attached during the body function to be detected.

It will, of course, be understood that various changes may be made in the form, details, arrangement and proportions of the parts without departing from the scope of our invention which consists of the matter shown and described herein and set forth in the appended claims.

We claim:

1. A body function sensor comprising:

(a) a. deflection device constructed and arranged to be supported and deflected about a transverse axis, said device extending longitudinally to define a longitudinal axis perpendicular to said transverse axis;

(b) a strain gauge fixedly fastened to said deflection device so that deflection of said strain gauge is obtained when said deflection device is deflected through a small increment about said transverse axis;

(0) holding means adapted to hold said deflection device against the body along its longitudinal axis in a deflected position when so applied to such a body;

(d) and electrical apparatus connected to said strain gauge to provide electrical signals representative of a temporary change in deflection of said strain gauge caused by a temporary change in such body volume due to a change in the body function to be sensed.

2. The invention as set forth in claim 1 including a jacket of readily deformable plastic material for covering said deflection member and said strain gauge to form a protective and insulative covering therefor.

3. A body function sensor comprising:

(a) a deflection device including a deflection member constructed and arranged to be supported and deflected about a transverse axis, said member extending longitudinally therefrom to define a longitudinal axis perpendicular to said transverse axis;

(b) a strain gauge fixedly fastened to said deflection member along said longitudinal axis so that maxi-. mum deflection of said strain gauge is obtained when said deflection member is deflected through a small increment about said traverse axis;

() binding material engaging said deflection device so that said deflection member is under moderate pressure along its longitudinal axis against a body member in a deflected position when so applied to such a body; and

(d) electrical apparatus connected to said strain gauge to detect a resistance change in said strain gauge representative of a temporary change therein caused by a temporary change in such body volume due to a change in the body function to be sensed.

4. A body function sensor comprising:

(a) a supporting member of flat and elongated elliptical shape having a central opening therein, one end of said supporting member including a bevelled edge sloping downward towards the bottom of said opening;

(b) a deflection member fixedly fastened at one end to said bevelled edge of said supporting member to extend downward and project through said central opening for deflection about said one end;

(0) a strain gauge fixedly fastened to said deflection member so that deflection of said strain gauge is obtained when said deflection member is deflected through a small increment;

(d) binding material cooperatively engaging said supporting member for holding said deflection member under moderate pressure against a body in a deflected position; and

(e) electrical apparatus connected to said strain gauge to provide electrical signals representative of a temporary change in deflection caused to saidstrain gauge by a temporary change in such body volume due to a change in the body function to be sensed.

5. Apparatus for detecting a body function comprising:

(a) a supporting device formed from a U shaped member and a cross member disposed in the open end of the 11 shaped member in which a bevelled edge sloping downward towards the bottom of said opening is formed;

(b) a cantilever member fixedly fastened to said bevelled edge of said cross member to extend downward and project through the central opening in said U shaped member for deflection about one end;

(c) a button shaped element fixedly connected to the end of said cantilever member so that said button extends below said cantilever member for engagement with the human body;

(d) a strain gauge fixedly fastened to said cantilever member so that deflection of said strain gauge is obtained when said cantilever member is deflected through a small increment;

(2) binding material fastened to said supporting U shaped member for holding said button shaped element under moderate pressure against such human body; and

(1) electrical apparatus connected to said strain gauge to provide electrical signals representative of a temporary change in deflection to said strain gauge caused by a temporary change in such body volume due to a change in the body function to be sensed.

6. A blood pulse sensor comprising:

(a) a supporting member of elongated elliptical shape having a central opening formed therein, one edge of said supporting member forming an edge of said central opening and having a bevelled edge sloping downwards towards the bottom of said opening;

(b) a deflection member fixedly fastened at one end to said bevelled edge of said supporting member, said member extending upward and away from said central opening;

(c) a lever cooperating with said deflection member to cause deflection thereof, said lever being supported for rotation within, and extending downward and projecting through said central opening to engage a body member;

(d) a strain gauge fixedly fastened to said deflection member so that deflection of said strain gauge is obtained when said deflection member is deflected through a small increment;

(e) releasable binding means for cooperatively engaging and holding said supporting member under moderate pressure against a body member so that said deflection member assumes a deflected position; and

(1) electrical apparatus connected to said strain gauge adaptedto provide electrical signals representative of a temporary chang in deflection caused by a temporary change in such body member volume due to a momentary change in such body blood pressure.

References Cited in the file of this patent UNITED STATES PATENTS 2,535,998 Bierman Dec. 26, 1950 2,753,863 Bailey July 10, 1956 2,848,992 Pigeon Aug. 26, 1958 2,854,968 Wright Oct. 7, 1958 2,875,750 Boucke Mar. 3, 1959 3,095,873 Edmunds July 2, 1963 

1. A BODY FUNCTION SENSOR COMPRISING: (A) A DEFLECTION DEVICE CONSTRUCTED AND ARRANGED TO BE SUPPORTED AND DEFLECTED ABOUT A TRANSVERSE AXIS, SAID DEVICE EXTENDING LONGITUDINALLY TO DEFINE A LONGITUDINAL AXIS PERPENDICULAR TO SAID TRANSVERSE AXIS; (B) A STRAIN GAUGE FIXEDLY FASTENED TO SAID DEFLECTION DEVICE SO THAT DEFLECTION OF SAID STRAIN GAUGE IS OBTAINED WHEN SAID DEFLECTION DEVICE IS DEFLECTED THROUGH A SMALL INCREMENT ABOUT SAID TRANSVERSE AXIS; (C) HOLDING MEANS ADAPTED TO HOLD SAID DEFLECTION DEVICE AGAINST THE BODY ALONG ITS LONGITUDINAL AXIS IN A DEFLECTED POSITION WHEN SO APPLIED TO SUCH A BODY; (D) AND ELECTRICAL APPARATUS CONNECTED TO SAID STRAIN GAUGE TO PROVIDE ELECTRICAL SIGNALS REPRESENTATIVE OF A TEMPORARY CHANGE IN DEFLECTION OF SAID STRAIN GAUGE CAUSED BY A TEMPORARY CHANGE IN SUCH BODY VOLUME DUE TO A CHANGE IN THE BODY FUNCTION TO BE SENSED. 